Statutory requirements provide an on-board diagnosis of toxic-emission relevant vehicle components such as catalytic converters.
Such an on-board diagnosis is known, for example, from U.S. Pat. No. 5,987,883. A correction of the conversion capability, which is determined with on-board means, for considering temperature influences on the diagnostic result is known from U.S. Pat. No. 5,526,643. Here, a diagnosis takes place only above a minimum temperature threshold.
There is further an interest to increase the quality and therewith the reliability of the diagnostic statements.